The aim of these studies is to visualize the macromolecular assemblies which form the structural basis of intracellular organelle translocation. The new electron microscopic technique of quick-freezing, deep-etching and rotary replication will be used to study these structural specializations. The three-demensional organization of the filamentous cytoskeleton, in which the force-generating and direct-governing entities probably reside, will be analyzed. Particular attention will be focused upon structures which have not been well illustrated by conventional electron microscopic methods. These include crosslinking structures between microtubules and organelles, possible specializations on membrane surfaces and filament attachments to membranes. The polarity of cytoskeletal filaments will be determined with a view to decide between the various hypotheses of organelle movement. Two model systems will be used - unmyelinated invertebrate axons and teleost melanophores. Images of cell interiors will be obtained under a variety of controlled transport conditions in the hopes of reconstructing the series of events during organelle translocation. Data obtained from these studies will help to explain how the cell transports, from one location to another, materials and information necessary for its maintenance.